number of legal restrictions on campaign contributions exist at both federal & state levels, latter regulations vary from state to state (and some of have none), among those in florida, for example, are $500 limits on both direct individual and group contributions to candidates and prohibition on contributions during last 5 days of campaigns...
federal election regulations (some of which folks are, no doubt, familiar with) include $2000 individual limits to a candidate, $5000 pac limits to a candidate, $5000 individual limits to a pac, $25,000 individual limits to a party, no cash contributions to candidates over $100 (btw: limits go up for candidates facing 'millionaire' candidates - allowed courtesy of mid-70s supreme court ruling in _buckley_, financing their campaigns with personal funds)...
initial legal limitations go back to so-called progressive era, federal and some state legislation banned banks & corporations from making direct contributions to candidates (enforcement was, admittedly, rare) those who thought watergate-era campaign finance 'reforms' would reduce influence/role of money were out to lunch, federal election campaign act (feca) *regime" provided money with legitimacy that it previously did not have (explanation, in large part, for under-the-table use), placed 'above ground' for all to see, campaign contribution is akin to market investment, in latter regard, feca has created 'paper trail' that can be tracked, which is of some importance...
re. legal restrictions on electioneering near polling places, those too can be traced to not-so/certainly not-always progressive era, intented to 'clean up' late 19th century election fraud & voter intimidation (oh yeah, and reduce working class/immigrant voting strength)...
check out poli sci guy richard bensel's _american ballot box in the mid-19th century_ for evidence/indication of how rowdy & raucous, hence, fun that election days could be, lots of booze & socializing (he also discusses extent of, among other things, vote buying, which liquor was, to some degree part of)...
one need not fetishize *fact* of late 19th century turnout rates exceeding those of recent decades given restriction of eligibility for blacks and women at that time, but consideration of *active" polling places ought to be taken seriously, several recent studies suggest that election day 'festivals' with food & entertainment & politicking may have positive impact on voter turnout... mh